A photolabile caged compound is a compound whose activity is inhibited, blocked or limited by the presence of one or more photolabile caging groups covalently associated with the compound. Exposure to light of an appropriate wavelength cleaves the caging group(s) from the compound, restoring its activity. A number of photolabile caged compounds have been (and are being) developed, including, for example, photolabile caged nucleotides, neurotransmitters, second messengers, and fluorescent dyes. Such photolabile caged compounds have been used, e.g., to examine various signaling pathways. However, the utility of such photolabile caged compounds (and other photoactivatable compounds) has been limited by lack of a convenient technology for uncaging the compounds reproducibly, uniformly, and safely, across various formats.
Devices that adapt microscopes for uncaging samples on microscope slides exist and are commercially available, e.g., from Photonic Instruments, Inc. (MicroPoint™ flash photolysis system, www.photonic-instruments.com); Cairn Research Ltd. (xenon arc flash photolysis system, www.caimweb.com); Rapp OptoElectronic (fiber optic flash photolysis system, www.rapp-opto.com); and Fryer Company, Inc. and Prairie Technologies, Inc. (fiber optic, UV, and laser photolysis systems; www.fryerco.com and www.prairie-technologies.com). However, these devices cannot uncage samples in multiwell plate, test tube, or other common laboratory formats. Devices such as xenon or mercury flash or ultraviolet (UV) lamps (e.g., Blak-Ray UV lamps from Spectronics Corporation, www.spectroline.com) can be used for uncaging, but the illumination provided by these devices (e.g., the optical energy density to which the sample is exposed) is typically not uniform or reproducible from use to use. In addition, such lamps typically have no safety features to prevent accidental exposure of a user to UV light, are not simple to use, and provide low energy light. Devices such as a RAYONET Photochemical Reactor (available from Southern N.E. Ultraviolet Co., Branford, Conn.) can be used for uncaging but, e.g., do not allow the wavelength or optical energy density to which the sample is exposed to be conveniently controlled. In U.S. Pat. No. 5,981,207 (Nov. 9, 1999), Burbaum et al. suggest that a microplate reader can be adjusted and used for uncaging, but the UV light produced by such readers typically has an inconveniently low optical power density.
The present invention provides uncaging devices that overcome the above noted and other difficulties. A complete understanding of the invention will be obtained upon review of the following.